1. Field of the Invention
This invention relates to an apparatus having an image blur correcting function for use in a video camera, a digital still camera or the like.
2. Related Background Art
Image pickup apparatuses (cameras) having a solid state image pickup element such as CCD on an imaging plane, such as video cameras and digital cameras, have heretofore been generalized. There are various sizes of image pickup elements such as CCD""s used in these image pickup apparatuses, and generally, as the number of pixels is increased, the size of the CCD becomes larger, and correspondingly, the cost increases. From these conditions, what is called xc2xc inch size, in which the diagonal length is in the order of 4 mm, or what is called ⅓ inch size, in which the diagonal length is in the order of 6 mm, is often conventionally used. Also the number of pixels of these CCD""s is generally 300,000 to 400,000.
Thus, the image size of these image pickup apparatuses is small compared with the 43 mm diagonal of a 135 film silver halide camera. Therefore, in lenses of the same angle of view, great downsizing is generally possible relative to the lenses of 135 film cameras. In fact, in video cameras using a CCD of xc2xc inch, a zoom lens having a zoom ratio of 10 and having a full length in the order of 50 mm is popular.
However, when such a zoom lens is mounted on a compact and light-weight video camera or digital still camera, there arises the problem that particularly in photographing wherein the focal length is set to a relatively long focus side, it is difficult due to hand vibration to obtain a stable image field. From such circumstances, various hand vibration preventing apparatuses have heretofore been proposed.
If a vibration preventing apparatus of this kind is used, not only the harmful vibration of the image field due to such hand vibration will be eliminated, but also a great effect will of course be achieved under such circumstances that in case of photographing from a ship or an automobile, harmful vibration cannot be eliminated even if a tripod is used.
The vibration preventing apparatus of this kind is provided with at least vibration detection means for detecting vibration, and blur correction means for effecting any correction in conformity with the information of the detected vibration so that blur may not occur as the image field.
As the vibration detection means, there are known, for example, an angular acceleration meter, an angular velocity meter, an angular displacement meter, etc. Also as the blur correction means, there are known optical means using a variable apex-angle prism or using the effect of shifting a part of a photo-taking optical system in a plane perpendicular to a photo-taking optical axis to bend the photo-taking optical axis as a result, and electronic means for sequentially changing (pursuing), in a video camera designed to cut out an area actually used as an image field from obtained image pickup image field information, the cutting-out position to a position in which vibration is corrected. However, the latter case is a correcting method among continuous image fields in a moving picture, and is not effective as the correction means in the case of a still picture.
Generally, optical correction means is capable of effecting correction to a vibration within an angle determined as the vibration correction angle of a camera irrespective of the focal length of the lens thereof, and accordingly, even when the focal length of a zoom lens on the telephoto side (the long focal length side) thereof is long, it is possible to have the capability of eliminating any vibration which poses no problem in practical use.
FIGS. 11A, 11B and 11C of the accompanying drawings illustrate the relation between the focal length and the vibration angle of a camera in the prior art at an object position on the image field. In FIG. 11A, the optical axis of the lens when the camera is at a position indicated by 112 is 113 and thus, the face of a person 111 which is an object is caught substantially at the center of the image field. Let it be assumed that from this state, the camera has been rotated through a degrees by hand vibration. The position of the camera at this time is indicated by 114 and the optical axis is indicated by 115.
FIGS. 11B and 11C show the position of the image field in this camera position indicated by 112 and 114, FIG. 11C shows the state of a zoom lens at the telephoto end (the end of the long focal length side), and FIG. 11B shows the state of the zoom lens at the wide end (the end of the short focal length side). The reference numeral 116 designates an object in the image field, the reference numerals 117 and 119 denote the respective image fields when the camera position is 112, and the reference numerals 118 and 120 designate the respective image fields when the camera position is 114.
As is apparent from FIGS. 11A to 11C, even if the camera vibration is of the same a degrees, the harm is greater as the vibration on the image field as a matter of course when the focal length of the lens is long. Accordingly, if it is combined with a lens having long focal length particularly on the telephoto side, the effect thereof is remarkable.
FIGS. 12A to 12C, 13A, 13B, 14 and 15 of the accompanying drawings show a construction using a variable apex-angle prism as an example of the blur correction means according to the prior art.
FIGS. 12A to 12C show the construction of the variable apex-angle prism itself. In these figures, the reference numerals 121 and 123 designate glass plates, and the reference numeral 127 denotes a bellows portion made of a material such as polyethylene. Transparent liquid 122 such as silicon oil is enveloped in the interior surrounded by the glass plates 123 and the bellows 127. In FIG. 12B, the two glass plates 121 and 123 are in a parallel state, and the angle of incidence and the angle of emergence of the ray of light of the variable apex-angle prism in this case are equal to each other. On the other hand, when as shown in FIGS. 12A and 12C, the glass plates have angles with respect to each other, the ray of light is bent at a certain angle as indicated by a ray of light 124 in FIG. 12A and a ray of light 126 in FIG. 12C.
Accordingly, vibration can be eliminated by controlling the angle of the variable apex-angle prism provided in front of a lens so that when the camera is inclined by a cause such as hand vibration, the ray of light may be bent by an amount corresponding to the angle of the inclination. FIGS. 13A and 13B show such state, and in FIG. 13A, assuming that the variable apex-angle prism becomes parallel and the ray of light catches the head of the object, there is shown a state in which by a correction for driving the variable apex-angle prism for a vibration of a degrees as shown in FIG. 13B to thereby bend the ray of light, the photo-taking optical axis still continues to catch the head of the object again in this case.
FIG. 14 shows an example of the actual construction of a variable apex-angle prism unit including a variable apex-angle prism and an actuator portion for driving it, and an apex-angle sensor for detecting an angle state. Actual vibrations appear in all directions and therefore, the front glass surface and rear glass surface of the variable apex-angle prism are designed to be rotatable with directions which are 90xc2x0 out of phase with each other as a rotational axis. Also, here, suffixes a and b indicate respective constituents in the two directions of rotation, and the constituents given the same reference numerals are entirely the same in function. Accordingly, description will hereinafter be made with the suffixes a and b omitted. The parts on the b side are partially not shown.
In FIG. 14, the reference numeral 141 designates a variable apex-angle prism comprising glass 121, 123, a bellows portion 127, a liquid, etc. The glass plates 121 and 123 are integrally attached to holding frames 128a, 182b with an adhesive agent or the like. Each holding frame 128a, 128b constituents a rotary shaft portion 133a, 133b between itself and a fixed part (not shown) and is rotatable about this shaft. The shafts 133a and 133b differ in direction by 90xc2x0 from each other. Each coil 135a, 135b is integrally provided on the holding frame 128a, 128b, respectively, while on the other hand, each magnet 136a, 136b, and yokes 137a, 137b and 138a, 138b are provided on a fixed portion (not shown). Accordingly, by electric current being supplied to coils 135a, 135b, the variable apex-angle prism 141 is rotated about its shafts 133a, 133b. There is a slit 129a in the tip end of an arm portion 130a integrally extending from the holding frame 128a, and an apex-angle sensor for detecting the angle state of the variable apex-angle prism is constituted between a light emitting element 131 a such as an iRED and a light receiving element 142a such as a PSD provided on the fixed portion.
FIG. 15 is a block diagram showing a vibration preventing apparatus provided with this variable apex-angle prism 141 as blur correction means, in combination with a lens.
In FIG. 15, the reference numeral 141 designates the variable apex-angle prism, the reference numerals 143 and 144 denote apex-angle sensors, the reference numerals 153 and 154 designate amplification circuits for amplifying the outputs of the apex-angle sensors to a predetermined level, the reference numeral 145 denotes a microcomputer, the reference numerals 146 and 147 designate vibration detection means constituted by angular velocity meters or the like, the reference numerals 148 and 149 denote actuators comprising the aforementioned coils 135a and 135b to the yokes 138a and 138b, respectively, and the reference numeral 152 designates a lens.
In the microcomputer 145, an electric current supplied to the actuators 148 and 149 is determined in order to control the variable apex-angle prism 141 to an angle state optimum to eliminate any vibration on the image field, in conformity with the angle state of the variable apex-angle prism 141 detected by the apex-angle sensors 143 and 144, and the result of the detection by the vibration detection means 146 and 147. The reason why in FIG. 15, the main blocks are shown as two systems is that it is assumed that the control in two directions which are 90xc2x0 out of phase with each other is individually effected.
Also, there have recently announced various forms of the layout of an image pickup apparatus such as a video camera or a digital still camera. Among them, there are nowadays particularly often seen image pickup apparatuses (cameras) of such layout in which a so-called camera portion including a photo-taking lens portion and a solid state image pickup element such as a CCD, and in the case of a video camera, a recorder portion comprising a mechanical portion for effecting recording and reproduction on a tape or the like, and a liquid crystal panel for displaying a recorded image and a reproduced image are rotatably constructed.
FIGS. 16A to 16C and FIGS. 17A and 17B of the accompanying drawings show video cameras of such conventional layout.
FIG. 16A is a front view of a video camera, FIG. 16B is a left side view thereof, and FIG. 16C is a right side view thereof. The reference numeral 240 designates a camera portion including at least a lens and a solid state image pickup element such as a CCD, the reference numeral 241 denotes a recorder portion which includes a recorder for recording an image photographed by a camera portion, the reference numeral 242 designates a photo-taking lens, the reference numeral 243 denotes a photo-taking optical axis, and the reference numeral 246 designates a coupling portion between the recorder portion and the camera portion which are rotatably coupled to each other. The reference numeral 248 denotes a liquid crystal panel as a viewfinder for displaying an image photographed by a camera portion as a finder image, and the reference numeral 247 designates the center of rotation of the liquid crystal panel. The camera portion 240 rotates about the center of rotation 246, and for example, becomes capable of photographing having an elevation angle like a state 245 indicated by dots-and-dark lines. And then optical axis is indicated by 244. Also, if the recorder portion 241 is rotated through 360xc2x0 relative to the lens portion 242 and the lens is turned toward a photographer, so-called face-to-face photographing will become possible. The liquid crystal panel rotates about a center of rotation 247, and can assume, for example, the state of a dots-and-dash position 249.
FIG. 17A is a front view of a video camera provided with a more compact camera portion, and FIG. 17B is a left side view thereof, and in this case, the camera portion 240 rotates about a center of rotation 246, and when it assumes the position of dots-and-dash lines 250, there can be realized an image pickup apparatus which is generally flat and excellent in portability.
Now, in the above-described examples of the prior art, when a photo-taking lens having optical blur correction means is used for blur correction and the piezo-electric vibration gyroscope or the like of an angular velocity meter for directly measuring the rotation of the camera is used as vibration detection means, an optimum construction has not been presented regarding the disposition of these detection means. For example, when the vibration detection means is disposed on the recorder side, a vibration in yaw direction (lateral vibration) as detected by the camera body when the camera portion is used while rotating relative to the recorder portion does not reflect the elevation angle of the camera portion and therefore, there is the problem that normal correction cannot be done unless the lateral vibration is corrected in accordance with the elevation angle of the camera and is replaced with the amount of movement of the blur correction means.
One aspect of the invention is an apparatus having the image blur correcting function which has a first unit including image blur correction means for correcting image blur, a second unit rotatable about a first axis differing from a photo-taking optical axis relative to the first unit, vibration detection means provided in the second unit for detecting the rotational vibration about the first axis, and control means for operating the image blur correction means in conformity with the output of the blur correction means, and which can effect normal image blur correction even when in a video camera or the like wherein only a camera portion is rotatable, only the camera portion has an elevation angle.
Another aspect of the invention is an apparatus having the image blur correcting function which has a first unit including image blur correction means for correcting image vibration, a second unit rotatable about a first axis differing from a photo-taking optical axis relative to the first unit, vibration detection means provided in the second unit for detecting rotational vibration about a second axis differing from both of the photo-taking optical axis and the first axis, signal correction means for correcting the output signal of second vibration detection means in conformity with the rotated state of the second unit relative to the first unit, and control means for operating the image blur correction means in conformity with a vibration signal obtained by the signal correction means, and which can effect normal image blur correction even when in a video camera or the like wherein only a camera portion is rotatable, only the camera portion has an elevation angle.
Another aspect of the invention is an apparatus having the image blur correcting function which has a first unit including image blur correction means for correcting image blur, a second unit rotatable about a first axis relative to the first unit, first vibration detection means provided in the second unit for detecting rotational vibration about the first axis, second vibration detection means provided in the first unit for detecting rotational vibration about a second axis differing from the first axis, and control means for operating the image blur correction means in conformity with the output signal of the first vibration detection means and the output signal of the second vibration detection means, and which can effect normal image blur correction even when in a video camera or the like wherein only a camera portion is rotatable, only the camera portion has an elevation angle.
Another aspect of the invention is an apparatus having the image blur correcting function which has a first unit including image blur correction means for correcting image blur, a second unit rotatable about a first axis relative to the first unit, first vibration detection means provided in the first unit for detecting rotational vibration about the first axis, second vibration detection means provided in the first unit for detecting rotational vibration about a second axis differing from the first axis, and a microcomputer provided in the second unit for operating the image blur correction means in conformity with the output signals of the first and second vibration detection means, and which can effect normal image blur correction even when in a video camera or the like wherein only a camera portion is rotatable, only the camera portion has an elevation angle.
Other objects and modes of the present invention will become apparent from the following detailed description of the invention.